Best way to protect against identity theft?

I've come across these two services, priced similarly, sound similar.

ID TheftSmart - The name sounds like they are a smart way to commit identity theft, but I suppose this is not what they mean.

Lifelock - Their tag line is "Guarantee your good name" and one of their gimmicks is that the CEO has published his SSN for all the world to see which is fairly daring and clever.

Do you know anything about the pros and cons of services like these, or the specifics of either or both of these?